Method and apparatus for rebalancing the sizes of the downlink (DL) association sets for component carriers having different time division duplex subframe configurations

ABSTRACT

Methods, apparatus and computer program products are provided for rebalancing the sizes of downlink (DL) association sets for component carriers having different time division duplex subframes configurations. A method is provided that includes determining DL subframes that are included in a DL association set for each of a plurality of component carriers. In an instance in which the number of acknowledgement (ACK)/negative acknowledgement (NACK) bits corresponding to the DL subframes included in the DL association sets for respective component carriers differ by at least a predetermined amount, the method modifies the number of ACK/NACK bits corresponding to the DL subframes that are included in the DL association sets for each of the respective component carriers. The method may also cause transmission of the ACK/NACK bits in accordance with the DL association sets, as modified, via the respective component carriers. Corresponding apparatus and computer program products are also provided.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of and claims priority to and thebenefit of U.S. patent application Ser. No. 14/678,456, filed Apr. 3,2015, which is a continuation of and claims priority to and the benefitof U.S. patent application Ser. No. 14/017,584, filed Sep. 4, 2013,which is a Continuation of and claims priority to and the benefit ofU.S. patent application Ser. No. 13/855,232 filed Apr. 2, 2013, which isin turn a Continuation of and claims priority to and the benefit of PCTInternational Patent Application No. PCT/CN2011/073529 filed on Apr. 29,2011, the entire content of each of which is incorporated herein byreference for all purposes.

TECHNOLOGICAL FIELD

Embodiments of the present invention relate generally to communicationstechnology and, more particularly, to methods and apparatus forrebalancing the sizes of the downlink (DL) association sets for aplurality of component carriers having different time division duplex(TDD) uplink (UL)/downlink (DL) subframe configurations.

BACKGROUND

Carrier aggregation is a combination of two or more cells or componentcarriers (CCs) operating at different frequencies in order to provide abroader transmission bandwidth for a mobile terminal. Depending upon itscapabilities, a mobile terminal may simultaneously receive or transmiton one or more of the cells. The cells aggregated in accordance withcarrier aggregation include a primary cell and one or more secondarycells. The primary cell is the component carrier that: (i) operates on aprimary carrier in which the mobile terminal either performs the initialconnection establishment procedure or initiates the connectionre-establishment procedure, or (ii) was indicated as the primary cell ina handover procedure, Conversely, a secondary cell is a componentcarrier, operating on a secondary carrier, which may be configured onceradio resource control (RRC) is established and which may be used toprovide additional radio resources.

Although the focus to date has been principally upon frequency divisionduplex (FDD) networks, TDD networks that support carrier aggregationmust also be considered. Indeed, in a TDD network, the primary cell andthe secondary cells may have respective TDD UL/DL subframeconfigurations. In Long Term Evolution (LTE) release 10, mobileterminals that support TDD signaling are required to operate inaccordance with a TDD UL/DL subframe configuration that is aligned andconsistent across the primary and secondary cells that are to beaggregated. Additionally, LTE release 10 required that commondiscontinuous reception (DRX) parameters be utilized for each of theprimary and secondary cells such that the active time and the DRXpattern would be the same for each of the aggregated cells.

For mobile terminals configured in accordance with LTE release 11,however, the primary and secondary cells are permitted to have differentTDD UL/DL subframe configurations. In this regard, primary and secondarycells having different TDD UL/DL subframe configurations may providedifferent amounts of resources and a different DL/UL ratio for themobile terminal. For example, the use of different TDD UL/DL subframeconfigurations by the primary and secondary cells in LTE release 11 maypermit different ones of the cells to provide different coverage by, forexample, enabling more UL subframes in a lower frequency cell to enlargethe coverage. The different TDD UL/DL subframe configurations may alsosupport inter-band carrier aggregation and coexistence with othersystems and certain frequency bands. The ability to provide differentamounts of resources and a different DL/UL ratio may be of particularimportance to a mobile terminal that utilizes carrier aggregation sincecarrier aggregation is oftentimes utilized in an instance in which themobile terminal has a relatively large amount of data to transmit,thereby increasing the importance of defining the TDD UL/DL subframeconfigurations of the primary and secondary cells so as to provide asuitable DL/UL ratio and to otherwise efficiently utilize thecommunication resources.

By allowing the primary and secondary cells to have different TDD UL/DLsubframe configurations, however, the different TDD UL/DL subframeconfigurations of the primary and secondary cells may have overlappedsubframes in some instances, such as by one of the cells having a DLsubframe at a specific instance in time while another cell has an ULsubframe. In order to avoid missing any transmission and receptionopportunities, a mobile terminal may be configured to provide forsimultaneous reception and transmission so as to accommodate overlappingsubframes.

The TDD UL/DL subframe configuration of a cell normally defines itshybrid automatic repeat request (HARD) timing and reception. Forexample, FIG. 1 illustrates a primary cell having TDD configuration #4and a secondary cell having TDD configuration #2. The uplink ACK/NACKfeedback may be provided by each of the primary and secondary cellsbased upon their respective configurations. In an instance in which thesecondary cell supports a physical uplink control channel (PUCCH),uplink frame #8 of the secondary cell may support transmission of anACK/NACK bit. Additionally, in downlink subframes #6, 7 and 8 of theprimary cell, physical downlink shared channel (PDSCH) may be supportedsince simultaneous transmission and reception is allowed by the mobileterminal. Further, in uplink subframes #3 of the primary and secondarycells, the PUCCH may be from the primary cell.

By way of example, FIG. 1 illustrates a situation in which the primaryand secondary cells are configured to have TDD UL/DL configurations #4and #1 respectively. In accordance with the UL ACK/NACK timing specifiedby the LTE specification, a number of DL subframes require UL ACK/NACKfeedback in UL subframe #3. Thus, the size of the DL association set forthe primary cell may be four, that is, downlink subframes #6, 7, 8 and9, and for the secondary cell may be one, that is, downlink subframe #9.Similarly, in an instance in which the downlink pilot time slot (DwPTS)does not support PDSCH transmissions, the size of the DL association setfor UL subframe #2 would be 3 and 1 for the primary cell and thesecondary cell, respectively. By having different numbers of downlinksubframes that require UL ACK/NACK feedback in a respective UL subframe,the primary and secondary cells may be unbalanced.

In an instance in which a mobile terminal is configured to support PUCCHformat 1b with channel selection mode b, that is, the PUCCH mode withACK/NACK time domain bundling, the ACK/NACK bits may be compressed bymapping the ACK/NACK bits to respective states. In this regard, Table 1presented below defines the mapping between various combinations of fourDL subframes, that is, a DL association set of size 4, and respectivestates. In this table, A represents ACK, N represents NACK, D representsdiscontinuous transmission (DTX) and “any” means that the states have tobe reported to or by the mobile terminal regardless of whether themobile terminal correctly received the corresponding state.

TABLE 1

As shown by the dashed blocks in Table 1, there will be DL throughput(TP) loss due to unnecessary retransmission for those states thatcorrespond to DL subframes designated as “any” since an “any” subframealways results in retransmission for the PDSCH.

The unbalanced scenario depicted in FIG. 1 having componentcarrier-specific TDD configurations may be required to co-exist withtime division synchronous code division multiple access (TD-SCDMA) inone of the bands. In this regard, the co-existence with TD-SCDMA willrequire TDD UL/DL configuration #1 or #2 in the relative frequency band.As shown in FIG. 1, the secondary cell has a TDD configuration #1, butthe other component carrier, that is, the primary cell, is configuredwith a TDD UL/DL configuration #4 for supporting improved downlinkthroughput in the cell. As such, the scenario depicted by FIG. 1 mayoccur with some frequency. As an example, if the PDCCH/PDSCH decodingperformance is independent among the DL subframes and the ACKprobability of a PDSCH is around 0.1 while the PDCCH DRX probability ismuch lower, then the probability of the state “A, A, N/D, any” is about8.1 percent and the probability of the state “N, any, any, any” is about10 percent. Thus, the DL TP loss that results from the imbalance in theDL association set sizes of two cells may occur more frequently thandesired.

BRIEF SUMMARY

Methods, apparatus and computer program products are provided accordingto an example embodiment for rebalancing the sizes of the downlink (DL)association sets for component carriers having different time divisionduplex subframe configurations. By rebalancing the sizes of the downlink(DL) association sets for component carriers having different TDDsubframe configurations, the TP loss may be reduced as a result of areduction in the number of retransmissions.

In one embodiment, a method is provided that includes determining DLsubframes that are included in a DL association set for each of aplurality of component carriers. In an instance in which the number ofacknowledgement (ACK)/negative acknowledgement (NACK) bits correspondingto the DL subframes included in the DL association sets for respectivecomponent carriers differ by at least a predetermined amount, the methodmodifies the number of ACK/NACK bits corresponding to the DL subframesthat are included in the DL association set for each of the respectivecomponent carriers. The method may also cause transmission of ACK/NACKbits in accordance with the DL association sets, as modified, via therespective component carriers.

In another embodiment, an apparatus is provided that includes at leastone processor and at least one memory including computer program codewith the at least one memory and the computer program code beingconfigured to, with the at least one processor, cause the apparatus atleast to determine DL subframes that are included in a DL associationset for each of a plurality of component carriers. In an instance inwhich the number of acknowledgement (ACK)/negative acknowledgement(NACK) bits corresponding to the DL subframes included in the DLassociation sets for respective component carriers differ by at least apredetermined amount, the at least one memory and the computer programcode are configured to, with the at least one processor, cause theapparatus to modify the number of ACK/NACK bits corresponding to the DLsubframes that are included in the DL association set for each of therespective component carriers. The at least one memory and the computerprogram code may also be configured to, with the at least one processor,cause the apparatus to cause transmission of ACK/NACK bits in accordancewith the DL association sets, as modified, via the respective componentcarriers.

In a further embodiment, a computer program product is provided thatincludes at least one computer-readable storage medium havingcomputer-executable program code instructions stored therein with thecomputer-executable program code instructions including program codeinstructions for determining DL subframes that are included in a DLassociation set for each of a plurality of component carriers. In aninstance in which the number of acknowledgement (ACK)/negativeacknowledgement (NACK) bits corresponding to the DL subframes includedin the DL association sets for respective component carriers differ byat least a predetermined amount, the computer-executable program codeinstructions include program code instructions for modifying the numberof ACK/NACK bits corresponding to the DL subframes that are included inthe DL association set for each of the respective component carriers.The computer-executable program code instructions may also includeprogram code instructions for causing transmission of ACK/NACK bits inaccordance with the DL association sets, as modified, via the respectivecomponent carriers.

In yet another embodiment, an apparatus is provided that includes meansfor determining DL subframes that are included in a DL association setfor each of a plurality of component carriers. In an instance in whichthe number of acknowledgement (ACK)/negative acknowledgement (NACK) bitscorresponding to the DL subframes included in the DL association set forrespective component carriers differ by at least a predetermined amount,the apparatus also includes means for modifying the number of ACK/NACKbits corresponding to the DL subframes that are included in the DLassociation set for each of the respective component carriers. Theapparatus may also include means for causing transmission of ACK/NACKbits in accordance with the DL association sets, as modified, via therespective component carriers.

In one embodiment, a method is provided that includes determining DLsubframes that are included in a DL association set for each of aplurality of component carriers. In an instance in which the number ofacknowledgement (ACK)/negative acknowledgement (NACK) bits correspondingto the DL subframes included in the DL association set for respectivecomponent carriers differ by at least a predetermined amount, the methodmodifies the number of ACK/NACK bits corresponding to the DL subframesthat are included in the DL association set for each of the respectivecomponent carriers. The method may also receive signals via therespective component carriers including ACK/NACK bits in accordance withthe DL association sets, as modified.

In another embodiment, an apparatus is provided that includes at leastone processor and at least one memory including computer program codewith the at least one memory and the computer program code beingconfigured to, with the at least one processor, cause the apparatus atleast to determine DL subframes that are included in a DL associationset for each of a plurality of component carriers. In an instance inwhich the number of acknowledgement (ACK)/negative acknowledgement(NACK) bits corresponding to the DL subframes included in the DLassociation set for respective component carriers differ by at least apredetermined amount, the at least one memory and the computer programcode are configured to, with the at least one processor, cause theapparatus to modify the number of ACK/NACK bits corresponding to the DLsubframes that are included in the DL association set for each of therespective component carriers. The at least one memory and the computerprogram code may also be configured to, with the at least one processor,cause the apparatus to receive signals via the respective componentcarriers including ACK/NACK bits in accordance with the DL associationsets, as modified.

In a further embodiment, a computer program product is provided thatincludes at least one computer-readable storage medium havingcomputer-executable program code instructions stored therein with thecomputer-executable program code instructions including program codeinstructions for determining DL subframes that are included in a DLassociation set for each of a plurality of component carriers. In aninstance in which the number of acknowledgement (ACK)/negativeacknowledgement (NACK) bits corresponding to the DL subframes includedin the DL association sets for respective component carriers differ byat least a predetermined amount, the computer-executable program codeinstructions include program code instructions for modifying the numberof ACK/NACK bits corresponding to the DL subframes that are included inthe DL association set for each of the respective component carriers.The computer-executable program code instructions may also includeprogram code instructions for receiving signals via the respectivecomponent carriers including ACK/NACK bits in accordance with the DLassociation sets, as modified.

In yet another embodiment, an apparatus is provided that includes meansfor determining DL subframes that are included in a DL association setfor each of a plurality of component carriers. In an instance in whichthe number of acknowledgement (ACK)/negative acknowledgement (NACK) bitscorresponding to the DL subframes included in the DL association set forrespective component carriers differ by at least a predetermined amount,the apparatus also includes means for modifying the number of ACK/NACKbits corresponding to the DL subframes that are included in the DLassociation set for each of the respective component carriers. Theapparatus may also include means for receiving signals via therespective component carriers including ACK/NACK bits in accordance withthe DL association sets, as modified.

The above summary is provided merely for purposes of summarizing someexample embodiments of the invention so as to provide a basicunderstanding of some aspects of the invention. Accordingly, it will beappreciated that the above described example embodiments are merelyexamples and should not be construed to narrow the scope or spirit ofthe invention in any way. It will be appreciated that the scope of theinvention encompasses many potential embodiments, some of which will befurther described below, in addition to those here summarized.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

Having thus described embodiments of the invention in general terms,reference will now be made to the accompanying drawings, which are notnecessarily drawn to scale, and wherein:

FIG. 1 illustrates the TDD UL/DL subframe configurations of a primarycell and a secondary cell having different DL association set sizes;

FIG. 2 illustrates a system including a mobile terminal and base stationconfigured to support TDD signaling and carrier aggregation inaccordance with one embodiment of the present invention;

FIG. 3 is a block diagram of a mobile terminal in accordance with oneembodiment of the present invention;

FIG. 4 is a block diagram of a base station in accordance with oneembodiment of the present invention;

FIG. 5 is a flowchart illustrating operations performed in the contextof a mobile terminal in accordance with one embodiment of the presentinvention; and

FIG. 6 is a flowchart illustrating operations performed in the contextof a base station or other network entity in accordance with oneembodiment of the present invention.

DETAILED DESCRIPTION

The present invention now will be described more fully hereinafter withreference to the accompanying drawings, in which some, but not allembodiments of the inventions are shown. Indeed, these inventions may beembodied in many different forms and should not be construed as limitedto the embodiments set forth herein; rather, these embodiments areprovided so that this disclosure will satisfy applicable legalrequirements. Like numbers refer to like elements throughout.

As used in this application, the term ‘circuitry’ refers to all of thefollowing: (a) hardware-only circuit implementations (such asimplementations in only analog and/or digital circuitry) and (b) tocombinations of circuits and software (and/or firmware), such as (asapplicable): (i) to a combination of processor(s) or (ii) to portions ofprocessor(s)/software (including digital signal processor(s)), software,and memory(ies) that work together to cause an apparatus, such as amobile phone or server, to perform various functions) and (c) tocircuits, such as a microprocessor(s) or a portion of amicroprocessor(s), that require software or firmware for operation, evenif the software or firmware is not physically present.

This definition of ‘circuitry’ applies to all uses of this term in thisapplication, including in any claims. As a further example, as used inthis application, the term “circuitry” would also cover animplementation of merely a processor (or multiple processors) or portionof a processor and its (or their) accompanying software and/or firmware.The term “circuitry” would also cover, for example and if applicable tothe particular claim element, a baseband integrated circuit orapplications processor integrated circuit for a mobile phone or asimilar integrated circuit in server, a cellular network device, orother network device.

A method, apparatus and computer program product are disclosed formodifying the number of ACK/NACK bits for a plurality of componentcarriers that have different TDD UL/DL subframe configurations. In thisregard, the method, apparatus and computer program product of someexample embodiments more closely balance the number of ACK/NACK bitscorresponding to the DL subframes in the DL association sets for theplurality of component carriers, thereby reducing the TP loss byreducing the number retransmissions. Although the method, apparatus andcomputer program product may be implemented in a variety of differentsystems, one example of such a system is shown in FIG. 2, which includesa first communication device (e.g., mobile terminal 10) that is capableof communication with a network 12 (e.g., a core network) via a basestation 14 (e.g., an evolved Node B (eNB)). While the network may beconfigured in accordance with LTE or LTE-Advanced (LTE˜A), othernetworks may support the method, apparatus and computer program productof embodiments of the present invention including those configured inaccordance with wideband code division multiple access (W˜CDMA),CDMA2000, global system for mobile communications (GSM), general packetradio service (GPRS) and/or the like.

The network 12 may include a collection of various different nodes,devices or functions that may be in communication with each other viacorresponding wired and/or wireless interfaces. For example, the networkmay include one or more base stations 14, such as one or more node Bs,eNBs, access points or the like, each of which may serve a coverage areadivided into one or more cells. The base station or other communicationnode could be, for example, part of one or more cellular or mobilenetworks or public land mobile networks (PLMNs). In turn, other devicessuch as processing devices (e. g., personal computers, server computersor the like) may be coupled to the mobile terminal and/or the secondcommunication device via the network. In accordance with embodiments ofthe present invention, the network may be a MD network,

A communication device, such as the mobile terminal 10 (also known asuser equipment (UE)), may be in communication with other communicationdevices or other devices via the base station 14 and, in turn, thenetwork 12. In instances in which the network is a TDD network, themobile terminal may be configured to support communications inaccordance with TDD. In some cases, the communication device may includean antenna for transmitting signals to and for receiving signals from abase station via a plurality of component carriers (CCs) including aprimary cell (Pcell) and one or more secondary cells (Scell). Asdescribed below, each of the primary and secondary cells may have a TDDUL/DL subframe configuration that defines a predefined sequence of DLsubframes, UL subframes and special (S) subframes to be exchangedbetween the mobile terminal and the network. The TDD UL/DL subframeconfigurations of the primary and secondary cells may be different suchthat there may be one or more overlapping subframes.

In some example embodiments, the mobile terminal 10 may be a mobilecommunication device such as, for example, a mobile telephone, portabledigital assistant (PDA), pager, laptop computer, or any of numerousother hand held or portable communication devices, computation devices,content generation devices, content consumption devices, or combinationsthereof. As such, the mobile terminal may include one or more processorsthat may define processing circuitry either alone or in combination withone or more memories. The processing circuitry may utilize instructionsstored in the memory to cause the mobile terminal to operate in aparticular way or execute specific functionality when the instructionsare executed by the one or more processors. The mobile terminal may alsoinclude communication circuitry and corresponding hardware/software toenable communication with other devices and/or the network 12.

In one embodiment, for example, the mobile terminal 10 may be embodiedas or otherwise include an apparatus 20 as generically represented bythe block diagram of FIG. 3. In the context of a mobile terminal, theapparatus may be configured to modify the number of DL subframes in theDL association sets for a plurality of component carriers that havedifferent TDD UL/DL subframe configurations, thereby permitting thenumber of DL subframes in the DL association sets to be more closelybalanced. While the apparatus may be employed, for example, by a mobileterminal, it should be noted that the components, devices or elementsdescribed below may not be mandatory and thus some may be omitted incertain embodiments. Additionally, some embodiments may include furtheror different components, devices or elements beyond those shown anddescribed herein.

As shown in FIG. 4, the apparatus 20 may include or otherwise be incommunication with processing circuitry 22 that is configurable toperform actions in accordance with example embodiments described herein.The processing circuitry may be configured to perform data processing,application execution and/or other processing and management servicesaccording to an example embodiment of the present invention. In someembodiments, the apparatus or the processing circuitry may be embodiedas a chip or chip set. In other words, the apparatus or the processingcircuitry may include one or more physical packages (e.g., chips)including materials, components and/or wires on a structural assembly(e.g., a baseboard). The structural assembly may provide physicalstrength, conservation of size, and/or limitation of electricalinteraction for component circuitry included thereon. The apparatus orthe processing circuitry may therefore, in some cases, be configured toimplement an embodiment of the present invention on a single chip or asa single “system on a chip.” As such, in some cases, a chip or chipsetmay constitute means for performing one or more operations for providingthe functionalities described herein.

In an example embodiment, the processing circuitry 22 may include aprocessor 24 and memory 26 that may be in communication with orotherwise control a device interface 28 and, in some cases, a userinterface 30. As such, the processing circuitry may be embodied as acircuit chip (e.g., an integrated circuit chip) configured (e.g., withhardware, software or a combination of hardware and software) to performoperations described herein. However, in some embodiments taken in thecontext of the mobile terminal 10, the processing circuitry may beembodied as a portion of a mobile computing device or other mobileterminal.

The user interface 30 (if implemented) may be in communication with theprocessing circuitry 22 to receive an indication of a user input at theuser interface and/or to provide an audible, visual, mechanical or otheroutput to the user. As such, the user interface may include, forexample, a keyboard, a mouse, a joystick, a display, a touch screen, amicrophone, a speaker, and/or other input/output mechanisms,

The device interface 28 may include one or more interface mechanisms forenabling communication with other devices and/or networks. In somecases, the device interface may be any means such as a device orcircuitry embodied in either hardware, or a combination of hardware andsoftware that is configured to receive and/or transmit data from/to anetwork 12 and/or any other device or module in communication with theprocessing circuitry 22. In this regard, the device interface mayinclude, for example, an antenna (or multiple antennas) and supportinghardware and/or software for enabling communications with a wirelesscommunication network and/or a communication modem or otherhardware/software for supporting communication via cable, digitalsubscriber line (DSL), universal serial bus (USE), Ethernet or othermethods.

In an example embodiment, the memory 26 may include one or morenon-transitory memory devices such as, for example, volatile and/ornon-volatile memory that may be either fixed or removable. The memorymay be configured to store information, data, applications, instructionsor the like for enabling the apparatus 20 to carry out various functionsin accordance with example embodiments of the present invention. Forexample, the memory could be configured to buffer input data forprocessing by the processor 24. Additionally or alternatively, thememory could be configured to store instructions for execution by theprocessor. As yet another alternative, the memory may include one of aplurality of databases that may store a variety of files, contents ordata sets. Among the contents of the memory, applications may be storedfor execution by the processor in order to carry out the functionalityassociated with each respective application. In some cases, the memorymay be in communication with the processor via a bus for passinginformation among components of the apparatus.

The processor 24 may be embodied in a number of different ways. Forexample, the processor may be embodied as various processing means suchas one or more of a microprocessor or other processing element, acoprocessor, a controller or various other computing or processingdevices including integrated circuits such as, for example, an ASIC(application specific integrated circuit), an FPGA (field programmablegate array), or the like. In an example embodiment, the processor may beconfigured to execute instructions stored in the memory 26 or otherwiseaccessible to the processor. As such, whether configured by hardware orby a combination of hardware and software, the processor may representan entity (e.g., physically embodied in circuitry—the form of processingcircuitry 22) capable of performing operations according to embodimentsof the present invention while configured accordingly. Thus, forexample, when the processor is embodied as an ASIC, FPGA or the like,the processor may be specifically configured hardware for conducting theoperations described herein. Alternatively, as another example, when theprocessor is embodied as an executor of software instructions, theinstructions may specifically configure the processor to perform theoperations described herein.

As noted above, a base station 14 or other network entity may beconfigured to communicate with the mobile terminal 10. In instances inwhich the network 12 is a TDD network, the base station may beconfigured to support communications in accordance with T D. In somecases, the base station may include an antenna for transmitting signalsto and for receiving signals from the mobile terminal via a plurality ofcomponent carriers including a primary cell and one or more secondarycells. As noted above, each of the primary and secondary cells may havea TDD UL/DL subframe configuration that defines a predefined sequence ofDL subframes, UL subframes and special (S) subframes to be exchangedbetween the mobile terminal and the network. The base station of oneembodiment may recognize that the number of ACK/NACK bits correspondingto the DL subframes in the DL association sets for a plurality ofcomponent carriers that have different TDD UL/DL subframe configurationshave been modified in such a manner as to permit the number of ACK/NACKbits corresponding to the DL subframes in the DL association sets to bemore closely balanced.

The base station 14 may include one or more processors that may defineprocessing circuitry either alone or in combination with one or morememories. The processing circuitry may utilize instructions stored inthe memory to cause the base station to operate in a particular way orexecute specific functionality when the instructions are executed by theone or more processors. The base station may also include communicationcircuitry and corresponding hardware/software to enable communicationwith the mobile terminal 10 and/or the network 12.

In one embodiment, for example, the base station 14 may be embodied asor otherwise include an apparatus 40 as generically represented by theblock diagram of FIG. 4. While the apparatus may be employed, forexample, by a base station, it should be noted that the components,devices or elements described below may not be mandatory and thus somemay be omitted in certain embodiments. Additionally, some embodimentsmay include further or different components, devices or elements beyondthose shown and described herein.

As shown in FIG. 4, the apparatus 40 may include or otherwise be incommunication with processing circuitry 42 that is configurable toperform actions in accordance with example embodiments described herein.The processing circuitry may be configured to perform data processing,application execution and/or other processing and management servicesaccording to an example embodiment of the present invention. In someembodiments, the apparatus or the processing circuitry may be embodiedas a chip or chip set. In other words, the apparatus or the processingcircuitry may include one or more physical packages (e.g., chips)including materials, components and/or wires on a structural assembly(e.g., a baseboard). The structural assembly may provide physicalstrength, conservation of size, and/or limitation of electricalinteraction for component circuitry included thereon. The apparatus orthe processing circuitry may therefore, in some cases, be configured toimplement an embodiment of the present invention on a single chip or asa single “system on a chip.” As such, in some cases, a chip or chipsetmay constitute means for performing one or more operations for providingthe functionalities described herein.

In an example embodiment, the processing circuitry 42 may include aprocessor 44 and memory 46 that may be in communication with orotherwise control a device interface 48. As such, the processingcircuitry may be embodied as a circuit chip (e.g., an integrated circuitchip) configured (e.g., with hardware, software or a combination ofhardware and software) to perform operations described herein. However,in some embodiments taken in the context of the base station 14, theprocessing circuitry may be embodied as a portion of a base station orother network entity.

The device interface 48 may include one or more interface mechanisms forenabling communication with other devices and/or networks. In somecases, the device interface may be any means such as a device orcircuitry embodied in either hardware, or a combination of hardware andsoftware that is configured to receive and/or transmit data from/to anetwork 12 and/or any other device or module in communication with theprocessing circuitry 42. In this regard, the device interface mayinclude, for example, an antenna (or multiple antennas) and supportinghardware and/or software for enabling communications with a wirelesscommunication network and/or a communication modem or otherhardware/software for supporting communication via cable, digitalsubscriber line (DSL), universal serial bus (USB), Ethernet or othermethods.

In an example embodiment, the memory 46 may include one or morenon-transitory memory devices such as, for example, volatile and/ornon-volatile memory that may be either fixed or removable. The memorymay be configured to store information, data, applications, instructionsor the like for enabling the apparatus 40 to carry out various functionsin accordance with example embodiments of the present invention. Forexample, the memory could be configured to buffer input data forprocessing by the processor 44. Additionally or alternatively, thememory could be configured to store instructions for execution by theprocessor. As yet another alternative, the memory may include one of aplurality of databases that may store a variety of files, contents ordata sets. Among the contents of the memory, applications may be storedfor execution by the processor in order to carry out the functionalityassociated with each respective application. In some cases, the memorymay be in communication with the processor via a bus for passinginformation among components of the apparatus,

The processor 44 may be embodied in a number of different ways. Forexample, the processor may be embodied as various processing means suchas one or more of a microprocessor or other processing element, acoprocessor, a controller or various other computing or processingdevices including integrated circuits such as, for example, an ASIC(application specific integrated circuit), an FPGA (field programmablegate array), or the like. In an example embodiment, the processor may beconfigured to execute instructions stored in the memory 46 or otherwiseaccessible to the processor. As such, whether configured by hardware orby a combination of hardware and software, the processor may representan entity (e.g., physically embodied in circuitry—in the form ofprocessing circuitry 42) capable of performing operations according toembodiments of the present invention while configured accordingly. Thus,for example, when the processor is embodied as an ASIC, FPGA or thelike, the processor may be specifically configured hardware forconducting the operations described herein. Alternatively, as anotherexample, when the processor is embodied as an executor of softwareinstructions, the instructions may specifically configure the processorto perform the operations described herein.

Referring now to FIGS. 5 and 6, flowcharts illustrating the operationsperformed by a method, apparatus and computer program product, such asapparatus 20 of FIG. 3 in regards to FIG. 5 and apparatus 40 of FIG. 4in regards to FIG. 6, in accordance with one embodiment of the presentinvention are illustrated. It will be understood that each block of theflowchart, and combinations of blocks in the flowchart, may beimplemented by various means, such as hardware, firmware, processor,circuitry and/or other device associated with execution of softwareincluding one or more computer program instructions. For example, one ormore of the procedures described above may be embodied by computerprogram instructions. In this regard, the computer program instructionswhich embody the procedures described above may be stored by a memorydevice of an apparatus employing an embodiment of the present inventionand executed by a processor in the apparatus. As will be appreciated,any such computer program instructions may be loaded onto a computer orother programmable apparatus (e.g., hardware) to produce a machine, suchthat the resulting computer or other programmable apparatus provides forimplementation of the functions specified in the flowchart block(s).These computer program instructions may also be stored in anon-transitory computer-readable storage memory that may direct acomputer or other programmable apparatus to function in a particularmanner, such that the instructions stored in the computer-readablestorage memory produce an article of manufacture, the execution of whichimplements the function specified in the flowchart block(s). Thecomputer program instructions may also be loaded onto a computer orother programmable apparatus to cause a series of operations to beperformed on the computer or other programmable apparatus to produce acomputer-implemented process such that the instructions which execute onthe computer or other programmable apparatus provide operations forimplementing the functions specified in the flowchart block(s). As such,the operations of FIGS. 5 and 6, when executed, convert a computer orprocessing circuitry into a particular machine configured to perform anexample embodiment of the present invention. Accordingly, the operationsof each of FIGS. 5 and 6 define an algorithm for configuring a computeror processing circuitry, e.g. processor 24, to perform an exampleembodiment. In some cases, a general purpose computer may be providedwith an instance of the processor which performs the algorithm of arespective one of FIGS. 5 and 6 to transform the general purposecomputer into a particular machine configured to perform an exampleembodiment.

Accordingly, blocks of the flowchart support combinations of means forperforming the specified functions and combinations of operations forperforming the specified functions. It will also be understood that oneor more blocks of the flowchart, and combinations of blocks in theflowchart, can be implemented by special purpose hardware-based computersystems which perform the specified functions, or combinations ofspecial purpose hardware and computer instructions.

As shown in block 50 of FIG. 5 from the context of a mobile terminal 10,an apparatus 20 according to one embodiment of the present inventionincludes means, such as the processing circuitry 22, the processor 24,the device interface 28 or the like, for determining the DL subframes,such as the number of DL subframes, that are included in a DLassociation set for each of a plurality of component carriers. In thisregard, a DL association set includes all of the DL subframes on arespective component carrier that need UL ACK/NACK feedback in arespective UL subframe. By way of an example, the component carriers mayinclude a primary cell and a secondary cell having respective DLassociation sets with N1 DL subframes and N2 DL, subframes,respectively. In this regard, the number of DL subframes in a DLassociation set for a component carrier having a predefinedconfiguration may be based upon the LTE release 8/9/10 UL ACK/NACKtiming specifications. As shown in block 52, the apparatus of thisembodiment may also include means, such as the processing circuitry, theprocessor or the like, for determining whether the number of ACK/NACKbits corresponding to the DL subframes in the DL association sets forthe component carriers differ by at least a predetermined amount. A DLsubframe may include one ACK/NACK bit or, in some embodiments, more thanone ACK/NACK bit. Thus, the determination as to the number of ACK/NACKbits corresponding to the DL subframes in the DL association sets may,in one embodiment in which each DL subframe includes a single ACK/NACKbit, also determine the number of DL subframes in the DL associationsets for the component carriers. While different predetermined amountsmay be established ha various embodiments, the processor of oneembodiment is configured to determine whether the number of ACK/NACKbits corresponding to the DL subframes in the DL association sets forthe component carriers differ by more than one. For example, in oneembodiment in which each DL subframe includes a single ACK/NACK bit andN1 and N2 represent the number of DL subframes in the DL associationsets for the primary cell and a secondary cell, respectively, theprocessor may determine that the difference between N1 and N2 is lessthan or equal to one, that is, N1−N2≤1, such that the number of DLsubframes in the DL association sets for the component carriers is notchanged, but is, instead, allowed to remain the same. Alternatively, inan instance in which the DL subframes in the DL association sets for thecomponent carriers are determined to differ by at least a predeterminedamount, such as by more than one, that is, N1−N2>1, the apparatus mayinclude means, such as the processing circuitry, the processor or thelike, for modifying the number of ACK/NACK bits corresponding to the DLsubframes that are included in the DL association set for each componentcarrier so as to at least partially remedy the imbalance. See block 54of FIG. 5.

The number of ACK/NACK bits corresponding to the DL subframes that areincluded in the DL association sets may be modified in various manners.In one embodiment, the number of DL subframes in the DL association setfor one component carrier, that is, the component carrier having the DLassociation set with fewer DL subframes, may be increased while thenumber of DL subframes in the DL association set for another componentcarrier, that is, the component carrier having a DL association set withmore DL subframes, may be decreased. In this regard, the number of DLsubframes in the DL association set for one component carrier may beincreased by the same number of DL subframes that the number of DLsubframes in the DL association set for the other component carrier isdecreased. In this embodiment, the number of DL subframes in the DLassociation set for one component carrier may be increased and thenumber of DL subframes in the DL association set for the other componentcarrier may be correspondingly decreased until the number of DLsubframes in the DL association sets for the respective componentcarriers differ by less than the predetermined amount, such as differingby no more than one.

As shown in block 56, the apparatus 20 of one embodiment may alsoinclude means, such as the processing circuitry 22, the processor 24 orthe like, for bundling the DL subframes of the component carriers basedupon the DL association sets, as modified. With reference to FIG. 1 inwhich a primary cell has a TDD configuration #4 and a secondary cell hasa TDD configuration #1, the primary cell may initially have four DLsubframes in its DL association set (as a result of DL subframes #6, #7,#8 and #9 requiring UL ACK/NACK in UL subframe #3) and the secondarycell may initially have one DL subframe in its DL association set (as aresult of DL subframe #9 requiring UL ACK/NACK in UL subframe #3.Without modification, the four DL subframes in the DL association set ofthe primary cell would be bundled, while the one DL subframe in the DLassociation set of the secondary set would be bundled. As a result ofthe unbalanced nature of the bundled DL subframes, performance loss willresult. In accordance with an embodiment of the present invention,however, following the modification of the number of DL subframes in theDL association sets of the component carriers, the DL subframes may bebundled in accordance with the resulting DL association sets. Inaccordance with the example of FIG. 1, the primary cell may have threeDL subframes in its DL association set and the secondary cell may havetwo DL subframes in its DL association set. As such, the three DLsubframes in the DL association set of the primary cell may be bundled.For example, subframes #6, #7 and #8 of the primary cell may be bundled.Additionally, the two DL subframes in the DL association set of thesecondary cell may be bundled. For example, subframe #9 of the secondarycell and subframe #9 of the primary cell may be bundled. Thus, DLsubframes may be bundled in accordance with one embodiment even thoughthe DL subframes are in different component carriers.

Component carriers having more than a predetermined number of DLsubframes in its DL association set, such as component carriers havingmore than two DL subframes in its DL association set, may be configuredto have the DL subframes compressed, such as in accordance with apredefined mapping. As shown in block 58, the apparatus 20 of oneembodiment may include means, such as the processing circuitry 22, theprocessor 24 or the like, for determining the mapped states of the DLsubframes of the DL association set for each respective carrier. Themapping may depend, for example, upon the number of DL subframes in a DLassociation set. In this regard, Tables 2 and 3 are provided below toshow examples of the mapping of three DL subframes in a DL associationset to corresponding states for each component carrier in Table 2 andfrom four DL subframes in a DL association set to corresponding statesfor each component carrier in Table 3.

TABLE 2 HARQ-ACK(0), HARQ-ACK(1), HARQ-ACK(2) Mapped state ACK, ACK, ACKACK, ACK ACK, ACK, NACK/DTX NACK/DTX, ACK ACK, NACK/DTX, any ACK,NACK/DTX NACK/DTX, any, any NACK/DTX, NACK/DTX

TABLE 3 HARQ-ACK(0), HARQ-ACK(1), Mapped HARQ-ACK(2), HARQ-ACK(3) state‘D, any, any, any’ or no DL assignment is received. D, D ‘A, D, D, D’ A,N ‘A, A, N/D, any’ N, A ‘A, A, A, N/D’ A, A ‘A, A, A, A’ A, N ‘N, any,any, any’ or ‘A, D/N, any, any except for A, D, D, D’ N, N

In one embodiment, there need not be any mapping in an instance in whichthe number DL subframes in a DL association set is two or less. However,in instances in which there are 3, 4 or more DL subframes in a DLassociation set, the DL subframes in a DL association set may be mappedto corresponding states, such as in accordance with the above exampletables. Based upon the mapped states of the DL association set for eachrespective component carrier and as shown in block 60 of FIG. 5, theapparatus 20 may also include means, such as the processing circuitry22, the processor 24, the device interface 28 or the like, for causingtransmission of the ACK/NACK bits in accordance with the DL associationset, as modified, via the respective component carriers.

With reference to the foregoing example in which three DL subframes,e.g., subframes #6, #7 and #8, that require an UL ACK bit in UL subframe#3 are bundled in accordance with the DL association set of the primarycell, the three DL subframes may be mapped to “ACK, ACK” pursuant toTable 2. Additionally, the two DL subframes, e.g., subframe #9 of thesecondary cell and subframe #9 of the primary cell, that are bundled inaccordance with the DL association set of the secondary cell need not bemapped and may retain their initial values, such as “ACK, NACK”. Tocomplete this example, the apparatus 20, such as the processor 24, maydetermine a PUCCH channel on UL subframe #3 based on the determinedstates, e.g., ACK, ACK, ACK, NACK, so as to provide the UL ACK/NACK.

As shown in FIG. 6 from the perspective of a base station 14, anapparatus 40 is configured to perform similar operations to thosedescribed above in conjunction with the apparatus 20 of the mobileterminal 10 in order to determine the manner in which the DL subframesof the DL association sets should be received for the respectivecomponent carriers. In this regard, the apparatus may include means,such as the processing circuitry 42, the processor 44, the deviceinterface 48 or the like, for determining the DL subframes, such as thenumber of DL subframes, that are included in a DL association set foreach of a plurality of component carriers, as shown in block 70 of FIG.6 and as described above in conjunction with block 50 of FIG. 5. Asshown in block 72, the apparatus of this embodiment may also includemeans, such as the processing circuitry, the processor or the like, fordetermining whether the number of ACK/NACK bits corresponding to the DLsubframes included in the DL association sets for the component carriersdiffer by at least a predetermined amount, such as by 1. In oneembodiment in which the number of ACK/NACK bits corresponding to the DLsubframes in the DL association sets for the primary cell and asecondary cell differ, if at all, by less than the predetermined amount,the number of DL subframes in the DL association sets for the componentcarriers is not changed, but is, instead, allowed to remain the same.Alternatively, in an instance in which the ACK/NACK bits correspondingto the DI, subframes in the DI, association sets for the componentcarriers are determined to differ by at least a predetermined amount,such as by more than one, the apparatus may include means, such as theprocessing circuitry, the processor or the like, for modifying thenumber of ACK/NACK bits corresponding to the DL subframes that areincluded in the DL association set for each component carrier so as toat least partially remedy the imbalance. See block 74 of FIG. 6 withexamples of the modification of the number of DL subframes in the DLassociation sets described above in conjunction with block 54 of FIG. 5.

As shown in block 76 and as described above in conjunction with block 56of FIG. 5, the apparatus 40 of one embodiment may also include means,such as the processing circuitry 42, the processor 44 or the like, forbundling the DL subframes of the component carriers based upon the DLassociation sets, as modified. As described in the context of a mobileterminal 10, component carriers having more than a predetermined numberof DL subframes in the DL association set, such as component carriershaving more than two DL subframes in the DL association set, may beconfigured to have the DL subframes in the DL association setcompressed, such as in accordance with a predefined mapping. As shown inblock 78, the apparatus of one embodiment may include means, such as theprocessing circuitry, the processor or the like, for determining themapped states of the DL subframes of each DL association set. Themapping may depend, for example, upon the number of DL subframes in theDL association sets, such as shown above in Tables 2 and 3.

As noted above, there need not be any mapping in an instance in whichthe number DL subframes in a DL association set is two or less. However,in instances in which there are 3, 4 or more DL subframes in the DLassociation set, the DL subframes of the DL association set may bemapped to a corresponding state. Based upon the mapped states of the DLsubframes in the DL association sets for each respective componentcarrier and as shown in block 80 of FIG. 5, the apparatus 40 may alsoinclude means, such as the processing circuitry 42, the processor 44,the device interface 48 or the like, for receiving the ACK/NACK bits inaccordance with the DL association set, as modified, via the respectivecomponent carriers.

By modifying the number of ACK/NACK bits corresponding to the DLsubframes in the DL association sets for the respective componentcarriers, the TP loss due to unnecessary retransmissions may beadvantageously reduced. For example, the numbers of DL subframes in theDL association sets for first and second component carriers designatedN1 and N2, respectively, may, for example, have ratios of N1:N2 of 4:1,4:2 and 3:1 which may be modified in accordance with embodiments of thepresent invention so as to be 3:2, 3:3 and 2:2. In instances in whichthe N1:N2 ratios of 4:1 and 3:1 are modified to ratios of 3:2 and 2:2,less bundling is required by the first component carrier so as to resultin less TP loss while the performance of the second component carrier isnot compromised.

In an instance in which the TDD UL/DL configuration for one of thecomponent carriers is reconfigured by the base station 14, there may bea time period during which the base station and mobile terminal 10 havedifferent understandings of the TDD configuration of the componentcarrier. During the time period in which this different understanding orambiguity exists, it may be difficult to map the DL subframes of DLassociation set to corresponding states, such as shown above in Tables 2and 3 since the size of the DL association set may be uncertain. In thisinstance, the base station may avoid any PDSCH scheduling during theperiod of ambiguity so that the mobile terminal will not report anyACK/NACK during this time period.

Many modifications and other embodiments of the inventions set forthherein will come to mind to one skilled in the art to which theseinventions pertain having the benefit of the teachings presented in theforegoing descriptions and the associated drawings. Therefore, it is tobe understood that the inventions are not to be limited to the specificembodiments disclosed and that modifications and other embodiments areintended to be included within the scope of the appended claims.Although specific terms are employed herein, they are used in a genericand descriptive sense only and not for purposes of limitation.

What is claimed is:
 1. A method comprising: determining downlink (DL)subframes that are included in a DL association set for each of aplurality of component carriers; in an instance in which a number ofacknowledgement (ACK)/negative acknowledgement (NACK) bits correspondingto the DL subframes included in the DL association sets for respectivecomponent carriers differ by at least a predetermined amount, modifyingthe number of ACK/NACK bits corresponding to the DL subframes that areincluded in the DL association set for each of the respective componentcarriers, wherein modifying the number of ACK/NACK bits corresponding tothe DL subframes that are included in the DL association set comprisesincreasing the number of DL subframes that are included in the DLassociation set for one component carrier until the number of DLsubframes that are included in the DL association sets for respectivecomponent carriers differ by less than the predetermined amount; andcausing transmission of ACK/NACK bits in accordance with the DLassociation set, as modified, via the respective component carriers. 2.The method according to claim 1, further comprising bundling DLsubframes of a plurality of component carriers based upon the DLassociation sets, as modified.
 3. The method according to claim 1,wherein causing transmission of the ACK/NACK bits comprises causingtransmission of the ACK/NACK bits to a base station, wherein the basestation is configured to recognize that the number of ACK/NACK bits hasbeen modified.
 4. The method according to claim 1, further comprisingdetermining a mapped state of the DL sub-frames of each respective DLassociation set.
 5. An apparatus comprising: at least one processor; andat least one memory including computer program code, wherein the atleast one memory and the computer program code are configured to, withthe at least one processor, cause the apparatus at least to perform:determining downlink (DL) subframes that are included in a DLassociation set for each of a plurality of component carriers; in aninstance in which a number of acknowledgement (ACK)/negativeacknowledgement (NACK) bits corresponding to the DL subframes includedin the DL association sets for respective component carriers differ byat least a predetermined amount, modifying the number of ACK/NACK bitscorresponding to the DL subframes that are included in the DLassociation set for each of the respective component carriers, whereinmodifying the number of ACK/NACK bits corresponding to the DL subframesthat are included in the DL association set comprises increasing thenumber of DL subframes that are included in the DL association set forone component carrier until the number of DL subframes that are includedin the DL association sets for respective component carriers differ byless than the predetermined amount; and causing transmission of ACK/NACKbits in accordance with the DL association set, as modified, via therespective component carriers.
 6. The apparatus according to claim 5,wherein the at least one memory and the computer program code arefurther configured to, with the at least one processor, cause theapparatus to bundle DL subframes of a plurality of component carriersbased upon the DL association sets, as modified.
 7. The apparatusaccording to claim 5, wherein the at least one memory and the computerprogram code are further configured to, with the at least one processor,cause the apparatus to determine a mapped state of the DL subframes ofeach respective DL association set.
 8. The apparatus according to claim5, wherein the apparatus comprises a mobile terminal.
 9. The apparatusaccording to claim 5, wherein the at least one memory and the computerprogram code are configured to, with the at least one processor, causethe apparatus to cause transmission of the ACK/NACK bits to a basestation, wherein the base station is configured to recognize that thenumber of ACK/NACK bits has been modified.
 10. The apparatus accordingto claim 5, further comprising a device interface configured tocommunicate with a base station including transmission of ACK/NACK bitsin accordance with the DL association set, as modified, via therespective component carriers.
 11. The apparatus according to claim 5,wherein the processor is configured for use in a Long Term Evolution(LTE) system.
 12. A method comprising: determining downlink (DL)subframes that are included in a DL association set for each of aplurality of component carriers; in an instance in which a number ofacknowledgement (ACK)/negative acknowledgement (NACK) bits correspondingto the DL subframes included in the DL association sets for respectivecomponent carriers differ by at least a predetermined amount, modifyingthe number of ACK/NACK bits corresponding to the DL subframes that areincluded in the DL association set for each of the respective componentcarriers, wherein modifying the number of ACK/NACK bits corresponding tothe DL subframes that are included in the DL association set comprisesincreasing the number of DL subframes that are included in the DLassociation set for one component carrier until the number of DLsubframes that are included in the DL association sets for respectivecomponent carriers differ by less than the predetermined amount; andreceiving signals via the respective component carriers includingACK/NACK bits in accordance with the DL association set, as modified.13. The method according to claim 12, further comprising bundling DLsubframes of a plurality of component carriers based upon the DLassociation sets, as modified.
 14. The method according to claim 12,further comprising determining a mapped state of the DL subframes ofeach respective DL association set.
 15. An apparatus comprising: atleast one processor; and at least one memory including computer programcode, wherein the at least one memory and the computer program code areconfigured to, with the at least one processor, cause the apparatus atleast to perform: determining downlink (DL) subframes that are includedin a DL association set for each of a plurality of component carriers;in an instance in which a number of acknowledgement (ACK)/negativeacknowledgement (NACK) bits corresponding to the DL subframes includedin the DL association sets for respective component carriers differ byat least a predetermined amount, modifying the number of ACK/NACK bitscorresponding to the DL subframes that are included in the DLassociation set for each of the respective component carriers, whereinmodifying the number of ACK/NACK bits corresponding to the DL subframesthat are included in the DL association set comprises increasing thenumber of DL subframes that are included in the DL association set forone component carrier until the number of DL subframes that are includedin the DL association sets for respective component carriers differ byless than the predetermined amount; and receiving signals via therespective component carriers including ACK/NACK bits in accordance withthe DL association set, as modified.
 16. The apparatus according toclaim 15, wherein the at least one memory and the computer program codeare further configured to, with the at least one processor, cause theapparatus to bundle DL subframes of a plurality of component carriersbased upon the DL association sets, as modified.
 17. The apparatusaccording to claim 15, wherein the at least one memory and the computerprogram code are further configured to, with the at least one processor,cause the apparatus to determine a mapped state of the DL subframes ofeach respective DL association set.
 18. The apparatus according to claim15, wherein the apparatus comprises a base station.
 19. The apparatusaccording to claim 15, further comprising a device interface configuredto communicate with a mobile terminal including receipt of ACK/NACK bitsin accordance with the DL association set, as modified, via therespective component carriers.
 20. The apparatus according to claim 15,wherein the processor is configured for use in a Long Term Evolution(LTE) system.